In a conventional composite writing implement, a plurality of desired writing shafts, such as ball pen writing shafts or mechanical pencil writing shafts, are housed in a barrel such that the front end of one of the writing shafts can be caused to project selectively from an opening provided in the front end of the barrel.
Conventional examples of this type of composite writing implement include a composite writing implement having a barrel formed from a front barrel and a rear barrel configured to be able to rotate relative to the front barrel, a cam main body configured to be not able to rotate relative to the rear barrel, and a slider configured to be not able to rotate relative to the front barrel and be coupled to a rear end portion of each writing shaft, wherein the cam main body is provided with a V-shaped cam projection projecting frontward, a cam surface extending along the cam projection so as to face frontward, and a latch portion provided on a part of the cam surface at an apex of the cam projection, the slider is provided with a V-shaped cam projecting rearward, and a sliding contact surface extending along the cam so as to face rearward, and when the sliding contact surface of the slider is pressed against the cam surface of the cam main body and the rear barrel and the front barrel are rotated relative to each other, a front end of a writing shaft is caused to project selectively from a front end opening in the barrel (see PTL 1).